4754. Humulon

Nomenclature

CAS number: 26472-41-3
(6R)-3,5,6-Trihydroxy-4,6-bis(3-methyl-2-butenyl)-2-(3-methyl-1-oxobutyl)-2,4-cyclohexadien-1-one; α-bitter acid; α-lupulic acid; humulone.
C21H30O5; mol wt 362.46.
C 69.59%, H 8.34%, O 22.07%.

Description and references

Antibiotic constituent of hops (Humulus lupulus L., Moraceae). See also Lupulon. Isoln from commercial hops: Bungener, Bull. Soc. Chim. [2] 45, 487 (1886); Barth, Lintner, Ber. 31, 2022 (1898); Wollmer, Ber. 49, 780 (1916); Lewis et al., J. Clin. Invest. 28, 916 (1949). Structure: Riedl, Ber. 85, 692 (1952); Carson, J. Am. Chem. Soc. 73, 4652 (1951). Absolute configuration and structure of preferred isomer: DeKeukeleire, Verzele, Tetrahedron 26, 385 (1970).

Chemical structure

Properties

Crystals from ether, mp 65-66.5°. Bitter taste, esp in alcoholic soln. More stable to air than lupulon. Monobasic acid. [α]D20 212° (1.0 g in 15.5 g 96% alc). uv max (ethanol): 237, 282 nm (ε 13,760; 8330). Soluble in the usual organic solvents. Slightly sol in boiling water from which it separates as a milky precipitate on cooling. Forms a sodium salt which is readily sol in water. Suffers no loss of bacteriostatic potency against Staphylococcus aureus upon autoclaving 40 ppm in phosphate buffer at pH 6.5 or 8.5. The presence of ascorbic acid in low concns extends the duration of bacteriostatic action.